Effect of addition of niobium oxide on the thermal conductivity of alumina

Santos, Wilson Nunes dos; Filho, P.I. Paulin; Taylor, R. E.

doi:10.1016/s0955-2219(98)80010-1

Cited by 21 publications

(16 citation statements)

References 6 publications

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“…Moreover, the interface between Nb and Al 2 O 3 should be stable at high temperatures in an inert atmosphere [12,13,14,15,16,17,18,19,20]. Mechanical properties [6,7,10,11], wear behavior [21], chemical stability [19,22] and thermal conductivity [23] of the sintered mixtures of Nb and Al 2 O 3 were reported only for components made of very fine powders. In particular, fine-grained tantalum-alumina composites were studied as a potential material for femoral head in total hip arthroplasty [24].…”

Section: Introductionmentioning

confidence: 99%

Mechanical High-Temperature Properties and Damage Behavior of Coarse-Grained Alumina Refractory Metal Composites

et al. 2019

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The present study provides the mechanical properties of a new generation of refractory composites based on coarse-grained Al2O3 ceramic and the refractory metals Nb and Ta. The materials were manufactured by refractory castable technology and subsequently sintered at 1600 °C for 4 h. The mechanical properties and the damage behavior of the coarse-grained refractory composites were investigated at high temperatures between 1300 and 1500 °C. The compressive strength is given as a function of temperature for materials with two different volume fractions of the refractory metals Ta and Nb. It is demonstrated that these refractory composites do not fail in a completely brittle manner in the studied temperature range. The compressive strength for all materials significantly decreases with increasing temperature. Failure occurred due to the formation of cracks along the ceramic/metal interfaces of the coarse-grained Al2O3 particles. In microstructural observations of sintered specimens, the formation of tantalates, as well as niobium oxides, were observed. The lower compressive strength of coarse-grained Nb-Al2O3 refractory composites compared to Ta-Al2O3 is probably attributed to the formation of niobium oxides. The formation of tantalates, however, seems to have no detrimental effect on compressive strength.

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Section: Introductionmentioning

confidence: 99%

Mechanical High-Temperature Properties and Damage Behavior of Coarse-Grained Alumina Refractory Metal Composites

et al. 2019

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“…Sendo assim, não houve pressão de vapor suficiente para uma variação de perda de massa mais perceptível. Por outro lado, nas amostras de Al 2 O 3 com Nb 2 O 5 o valor foi de 2,6%, provavelmente pela volatilização do AlNbO 4 [18].…”

Section: Resultsunclassified

Síntese e caracterização do compósito Al2O3 -YAG e do Al2O3-YAG e Al2O3 aditivados com Nb2O5

et al. 2012

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O compósito Al2O3-YAG possui alta resistência à corrosão e à fluência em ambientes agressivos, o que permite vislumbrar aplicações bastante atrativas, tais como aletas de motores a jato e de turbinas a gás. Este compósito também apresenta elevada dureza e alta resistência à abrasão possibilitando o seu emprego em blindagens balísticas. Nesse estudo os pós precursores de Al2O3, Y2O3 e Nb2O5 foram homogeneizados em moinho de bolas planetário por 4 h, secados em estufa a 120 ºC por 48 h, desaglomerados e peneirados. O compósito Al2O3-YAG foi produzido a partir das misturas de Al2O3-Y2O3 a 1300 ºC por 2 h. Foram produzidas amostras de Al2O3-YAG, Al2O3-YAG com Nb2O5 e Al2O3 com Nb2O5. Posteriormente os pós foram prensados uniaxialmente a 70 MPa. A sinterização foi feita a 1400 e 1450 ºC. Os pós como recebidos e os processados foram caracterizados quanto à área de superfície específica e ao tamanho médio de partícula. Os materiais sinterizados foram caracterizados por densidade e porosidade aparente pelo método de Arquimedes e avaliados quanto à retração e à perda de massa. Os resultados mostraram que são necessários ainda ajustes nas condições de sinterização da composição Al2O3-YAG com Nb2O5 para melhorar a densificação e a retração, que foram baixas, da ordem de 60 e 3%, respectivamente. O Al2O3 aditivado com Nb2O5, por sua vez, apresentou uma densificação satisfatória, de 96% e uma retração em torno de 15%.

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“…2c shows that the shell is amorphous; and Fig. 2d presents the lattice fringes of Al2O3 (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13) and (-114) planes with interplanar spacing of about 0.201 nm and 0.259 nm, respectively, indicating that the core is Al2O3 crystalline. This result verifies that a uniform amorphous deposition was formed on the surface of the Al2O3 particle.…”

Section: Characterization Of Cp Processed Al 2 O 3 Powdermentioning

confidence: 98%

“…In the present work, the thermal conductivity of Sample AL was determined by taking the specific heat capacity value of the high purity Al2O3 ceramics (0.755 J•g -1 •K -1 at room temperature) [47]. Y2O3 doping can result in the formation of a second phase (yttrium aluminum garnet, YAG) in Al2O3 ceramic [37], and the specific heat capacities of the Y2O3-Al2O3 system (Samples MM and CP) were calculated by using the Neumann-Kopp rule [48]:…”

Section: Characterizationmentioning

confidence: 99%

Microstructure refinement - homogenization and flexural strength improvement of Al2O3 ceramics fabricated by DLP-stereolithography integrated with chemical precipitation coating process

Nie

Sheng

et al. 2020

Preprint

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In this study, the chemical precipitation coating (CP) process was creatively integrated with DLP-stereolithography based 3D printing for refining and homogenizing the microstructure of 3D printed Al2O3 ceramic. Based on this novel approach, Al2O3 powder was coated with a homogeneous layer of amorphous Y2O3; with the coated Al2O3 powder found to make the microstructure of 3D printed Al2O3 ceramic more uniform and refined, as compared with the conventional mechanical mixing (MM) of Al2O3 and Y2O3 powders. The grain size of Al2O3 in Sample CP is 64.44% and 51.43% lower than those in the monolithic Al2O3 ceramic (AL) and Sample MM, respectively. Sample CP has the highest flexural strength of 455.37±32.17 MPa, which is 14.85% and 25.45% higher than those of Samples MM and AL, respectively; also Sample CP has the highest Weibull modulus of 16.88 among the three kinds of samples. Moreover, the fine grained Sample CP has a close thermal conductivity to the coarse grained Sample MM because of the changes in morphology of Y3Al5O12 phase from semi-connected (Sample MM) to isolated (Sample CP). Finally, specially designed fin-type Al2O3 ceramic heat sinks were successfully fabricated via the novel integrated process, which has been proven to be an effective method for fabricating complex-shaped Al2O3 ceramic components with enhanced flexural strength and reliability.

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Effect of addition of niobium oxide on the thermal conductivity of alumina

Cited by 21 publications

References 6 publications

Mechanical High-Temperature Properties and Damage Behavior of Coarse-Grained Alumina Refractory Metal Composites

Mechanical High-Temperature Properties and Damage Behavior of Coarse-Grained Alumina Refractory Metal Composites

Síntese e caracterização do compósito Al2O3 -YAG e do Al2O3-YAG e Al2O3 aditivados com Nb2O5

Microstructure refinement - homogenization and flexural strength improvement of Al2O3 ceramics fabricated by DLP-stereolithography integrated with chemical precipitation coating process

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